Such terminal blocks currently equip telephone distribution frames in which they serve to connect, on request, the different monopair lines of the Telephone Distribution Company to the different corresponding lines of subscribers. There are several hundreds, and even several thousands of them.
These prior art terminal blocks all comprise at least two parallel rows of substantially flat metal contacts, placed opposite from one row to the other, these metal contacts each being provided with an axial slot for insulation-displacing connection of the wires to be connected. A contact of this type is for example described in document FR-A-2 330 159.
The contacts of the same row are coplanar. The contacts of the two parallel rows mentioned above are identical.
Each contact of one of these two conjugate rows is connected, to ensure continuity of the two lines, to the contact conjugate with respect to (i.e. opposite) the other row by a metal link which is either a link presenting a possibility of cut, in which case it is question of conjugate contacts "with cut", or a direct link without possibility of cut, in which case it is question of conjugate contacts in "U" form.
One of these two conjugate contacts is called "input contact", as it receives one of the two wires of the incoming line (coming from the Telephone Distribution Company), while the other contact is called "output contact", as it receives the corresponding wire of the two-wire outgoing line (i.e. the subscriber's line).
On each row among these two opposite rows, there is found a determined number of pairs of adjacent contacts, this number of pairs depending on the width of the terminal block.
Each pair of contacts is used for receiving the two wires of a telephone line, i.e. of the incoming line for the row containing the above-mentioned input contacts, and of the outgoing line for the row containing the said output contacts.
The substantially flat contacts which equip the terminal blocks presently marketed by Applicants are fairly similar to the one forming the subject matter of document FR-A-2 330 159 and in particular to the one shown in FIG. 1 of that document. Of course, such a contact comprises the principal part which is flat and of generally fixed width, which contains the insulation-displacing slot, and this principal part extends by a part of substantially the same width, which will be referred to as "extension" and which serves here to connect this contact to the conjugate contact mentioned above, i.e. to the contact which lies opposite on the other row.
When it is question of a link with cut, this extension is elastic and it comprises, at its free end, a stud for contact with the identical elastic conjugate extension of the conjugate contact opposite it. When it is question of a link in U form, this extension is common to that of this conjugate contact, with which it therefore constitutes a linking bridge made in one piece.
With the present increase in the operational frequencies of telephone and computer-related installations, a problem is raised, for these terminal blocks, of the rate of near end crosstalk between two adjacent pairs, the current terminal blocks of the prior art no longer complying with the standards of rejection of near end crosstalk which are now in force and which are much more strict than the standards which are applied to the terminal blocks of the prior art mentioned above.
To give an idea, for frequencies which may go up to 100 Megahertz, a rate of rejection of near end crosstalk between adjacent pairs which is greater than 40 dB is now required, whereas a rate of rejection of near end crosstalk merely greater than 20 dB was accepted in the past.
Manufacturers must in that case:
either increase the distance between two adjacent pairs on the same row of contacts, which has for a drawback either of increasing the dimensions of the terminal block for the same number of pairs, or of reducing the number of pairs if the same dimensions are conserved for this terminal block, PA1 or, as for example described in document EP-A-0 637 097 and EP-A-0 654 851, to reduce the dimensions of each contact in width to a maximum, this having for a drawback to render the latter more fragile than desired in order to obtain good reliability.
It is an object of the present invention to overcome these drawbacks.